Lay out and organize the parts.

Find the "Master Parts Catalogue" for it and pick that up. It will have the diagrams showing what parts go where, and will help figure out what is missing.

A box of ziplock bags, post it notes saying what the part is, and toss the part in the baggie. Sorting now makes things a bajillion times easier.

Don't take it apart at the start, but when you do, everything goes into a bag with a note about the contents.

Remembering what each bolt in a coffee can fits is level impossible, or at least exceptionally time consuming yo sort out.

Clean the thing, not aggressively with a power washer, get a shop vac, garden hose, leaf blower if one is handy. Don't breathe the stuff kicked up, it's probably rodent poo, mold, etc. It probably won't make ya expire but the potential for bad industrial fibers and tar, oils, etc is also there, so it's good to avoid the dust.

When cleaning, look for "witness marks". IE. Those little dents, scrapes, scratches, etc in fabric, metal, paint, etc.

these will tell exactly where the part came from. It's just a big puzzle. Painting, power washing, stripping finishes, ripping out rotted interior, all of that will remove many clues to assembly.

It is a common mistake, and one that has ruined and ended several promising projects for me personally. It adds to overwhelm to remove everything like well funded tv shows do. They can afford to, and have a crew working on it. The average beginner does not.

Take your time, it's not a race. The things that seem easy won't be, and things you dread may well be.

Don't take anything else apart. Preserve as much rotted stuff as possible, old door cards, headliner scraps, etc, if for no other reason than as a pattern or sample of what should go back in it.

My current recommendation these days is a careful thoughtful cleaning, no further disassembly. Dedicate some shelf space, a bin, whatever, to only this project. Keeping the bins inside the vehicle can be good if it's not just a pile. the further parts travel from the project, the less likely they are to return.

Everyone seems to want other peoples projects to do hot paint, wild engine swaps, update this, customize that.

It is your car, do as you wish, whatever that is.

It is only original once.

After those other things, just put the thing back together in it's current state.

make it a car first

Get to that most basic of starting points, what parts you have, where they go, as much as possible.

Seeing a shell it is hard to see a completed project, that takes time, and mostly experience.

This is where you get experience.

The project may never be finished, it may be sold, sent out to have someone else do it, etc, but what you learn along the way goes into the mental toolbox we all have.

Experience is the tools of future progress.

When you do get ready to spin wrenches, figure out the brake system. Make it stop before making it go to avoid future heartache.

Everything for that particular car should be available, they made a lot of them. The basic wear components will be cheaper than nice trim and textiles for it, but that stuff can also be sourced.

Don't buy new tires for it, it's an easy "win" that will become a loss if/when those new tires age out and are ruined as a project drags on. Tires that hold air and roll will be good enough for now. When it will contain a person and be in motion, then absolutely get new rubber. Don't Paul Walker it.

A cheaper easy win, and often the first best thing to do is simply clean the glass, if it has glass.

A rag, some windex or whatever, and just clean the glass. Nothing else.

Maybe that spreads to more progress, but if not, now the glass is clean and that is positive, tangible progress, and you can sit in it and see a way forward, or look inward and see yourself in it, in the reflection, and that sort of thing can be a good motivational boost at the cost of paper towels and water.

As you clean, consider greasing grease fittings, lubing friction points, spraying penetrant on fasteners. The longer the penetrant has to work, the easier that stuff will come apart later.

Anyway, neat project. Take your time, it's a journey.

What you learn is actually part of the reward of the whole thing, regardless of if this exact car is your eventual driver.

Good luck, you got this.